Ideas are among the most important items in Cartesian philosophy. They serve to unify Descartes' ontology and epistemology. As he says in a letter to Guillaume Gibieuf (1583–1650), dated 19 January 1642, “I am certain that I can have no knowledge of what is outside me except by means of the ideas I have within me.” Descartes never produced any formal treatise or work dedicated specifically to the laying out of a theory of ideas. Even so, enough is included in published and unpublished work, as well as in correspondence, that allows for a basic reconstruction of a theory. This entry will focus principally on the theory of ideas and how it relates to Descartes' ontology. See the related entry Descartes, Ren?: epistemology for more on how the theory relates to Descartes' epistemology.
The Renaissance, that is, the period that extends roughly from the middle of the fourteenth century to the beginning of the seventeen century, was a time of intense, all-encompassing, and, in many ways, distinctive philosophical activity. A fundamental assumption of the Renaissance movement was that the remains of classical antiquity constituted an invaluable source of excellence to which debased and decadent modern times could turn in order to repair the damage brought about since the fall of the Roman Empire. It was often assumed that God had given a single unified truth to humanity and that the works of ancient philosophers had preserved part of this original deposit of divine wisdom. This idea not only laid the foundation for a scholarly culture that was centered on ancient texts and their interpretation, but also fostered an approach to textual interpretation that strove to harmonize and reconcile divergent philosophical accounts. Stimulated by newly available texts, one of the most important hallmarks of Renaissance philosophy is the increased interest in primary sources of Greek and Roman thought, which were previously unknown or little read. The renewed study of Neoplatonism, Stoicism, Epicureanism, and Skepticism eroded faith in the universal truth of Aristotelian philosophy and widened the philosophical horizon, providing a rich seedbed from which modern science and modern philosophy gradually emerged.
This entry discusses philosophical idealism as a movement chiefly in the eighteenth and nineteenth centuries, although anticipated by certain aspects of seventeenth century philosophy. It examines the relationship between epistemological idealism (the view that the contents of human knowledge are ineluctably determined by the structure of human thought) and ontological idealism (the view that epistemological idealism delivers truth because reality itself is a form of thought and human thought participates in it). After discussing precursors, the entry focuses on the eighteenth-century versions of idealism due to Berkeley, Hume, and Kant, the nineteenth-century movements of German idealism and subsequently British and American idealism, and then concludes with an examination of the attack upon idealism by Moore and Russell.
Plato (429?–347 B.C.E.) is, by any reckoning, one of the most dazzling writers in the Western literary tradition and one of the most penetrating, wide-ranging, and influential authors in the history of philosophy. An Athenian citizen of high status, he displays in his works his absorption in the political events and intellectual movements of his time, but the questions he raises are so profound and the strategies he uses for tackling them so richly suggestive and provocative that educated readers of nearly every period have in some way been influenced by him, and in practically every age there have been philosophers who count themselves Platonists in some important respects. He was not the first thinker or writer to whom the word “philosopher” should be applied. But he was so self-conscious about how philosophy should be conceived, and what its scope and ambitions properly are, and he so transformed the intellectual currents with which he grappled, that the subject of philosophy, as it is often conceived—a rigorous and systematic examination of ethical, political, metaphysical, and epistemological issues, armed with a distinctive method—can be called his invention. Few other authors in the history of Western philosophy approximate him in depth and range: perhaps only Aristotle (who studied with him), Aquinas, and Kant would be generally agreed to be of the same rank.